1. Field of the Invention
Method for calibrating a vacuum level for a web-based image forming system and an image forming system.
2. Description of Background Art
Within wide format inkjet printing the media encounters increasing friction as the leading edge shifts over a medium support surface positioned below the print head(s). The medium support surface comprises a plurality of vacuum holes through which air may be sucked towards a suction unit, such as a vacuum pump or fan. Generally, a drive roller is arranged for pushing the web stepwise over the medium support surface. An excess suction force applied by the operator may then result in the deformation of the web. An insufficient suction force, however, may result in the web coming into contact with the print head. This so-called “head touch” may possibly damage the print head. Properties of the medium affect its behavior during transport, for example stiffness of the medium, porosity, its curl, or its tendency to curl. The medium's properties may in turn be affected by the atmospheric conditions, such as humidity and temperature. In practice the above mentioned behavior varies considerably with various media. Further, at the start of a print operation, as the leading edge of the web is “lead in” over the support surface, the web stepwise covers an increasing number of the vacuum holes, which vacuum holes exert a varying, generally increasing, suction force on the leading edge. This interplay of effects influences the step size. Since the image is printed in consecutive swaps, variations in step size will result in the consecutive overlapping swaths of the image becoming misaligned with respect to one another. Thereby, the printed image becomes disturbed and the print quality is reduced.